On a course softened by rain earlier in the week, McIlroy shot a 5-under 67 to finish behind leader Carl Pettersson. Joost Luiten, who was 5-under through 17, had earlier threatened the tournament's 18-hole scoring record at 8 under through 14 holes. Tiger Woods looked sharp while making three straight birdies but had to settle for a 69 after an uneven round.

Pettersson finished at a 6-under 66, a stroke ahead of McIlroy and Gary Woodland (67). John Daly and defending champion Keegan Bradley both shot 68.

"I really felt like we had to take advantage of the conditions," McIlroy said. "I'm expecting this to be the best day of the week."

Thunderstorms were possible later Thursday and throughout the tournament, but skies were mostly clear when the first groups teed off. McIlroy is trying to break an unusual pattern in which the last 16 majors have been won by 16 different players. He tied for 40th at this year's Masters, missed the cut at the U.S. Open and tied for 60th at the British Open.